In the application of paints and other organic coating materials to metal surfaces or plastic surfaces, for example in the automotive industry, it is not possible to apply the paints or coating materials completely to the parts to be coated. So-called overspray collects in the paint spraying booths, particularly in the painting of motor vehicles, and is taken up with water and flushed into so-called system basins. In order, on the one hand, not to disturb the operation of water-carrying pipe, nozzle and sprinkler systems, for example by tacky paint particles, and other hand to free the circulating water from the paint ingredients taken up, chemicals known as coagulants have to be added to the circuit water to coagulate the ingredients in question.
Various neutral and alkaline products are available for denaturing and coagulating conventional paints, above all paints used in the automotive industry.
In known process for coagulating paints and coating materials, the technical installations present largely determine whether a paint coagulant which floats the coagulate in the settling basin is used or whether a coagulant which sediments the coagulate is used. In the first case, the coagulate can be stripped from the surface of the water whereas, in the second case, the sedimented coagulates are removed from the bottom of the basin by means of a scraping belt. However, paint disposal lines where the denatured paint particles have to be kept in a uniform dispersion or suspension in the circuit water without precipitating the paint are being used to increasing extent. Accordingly, depending on the type and quality of paint, the specific behavior of the paint particles has to be influenced in each individual case in such a way that paint particles with a tendency towards flotation or sedimentation form a uniform dispersion or suspension. An overview of the problems involved in the coagulation of paints is provided by J. Geke in "Oberflache+JOT", 1986, No. 11, pages 43 to 46.